The present invention relates to a rotary head type helical scanning system digital magnetic recording method, recording apparatus, reproducing apparatus, and recording/reproducing apparatus. More particularly, the invention concerns a digital recording method, recording apparatus, reproducing apparatus, and recording/reproducing apparatus, which have a track format suitable for selectively recording and/or reproducing either of two kinds of digital video signals including different amounts of information.
To show a set of two digital video signals with different amounts of information, one is a digital video signal of the 525-line/60-field system or the 625-line/50-field system (hereafter referred to as the current digital video signal), and the other is a high definition (HD) digital video signal of the 1125-line/60-field system (hereafter referred to as the HD digital video signal).
At present, as recording apparatus of the current digital video signal, so-called D1-VTR, D2-VTR, etc. arrangements have been put into practical business use. With regard to the D1 format for the D1-VTR and the D2 format for the D2-VTR, description has been made in "Television Gakkai-Shi" (the Journal of the Institute of Television Engineers of Japan), Vol. 42, No. 4 (April, 1988), pp. 338-346. As regards the recording apparatus of the HD digital video signal, a digital VTR using a one-inch tape has been used for business purposes. However, a digital VTR has not been created which can record and reproduce both the current digital video signal and the HD digital video signal as a single compatible apparatus.
When an assumption is made that a home-use digital VTR is produced which is compatible with high definition television (HDTV) broadcasting expected to come into a full-fledged operation in the near future, it is naturally desired that the digital VTR can record and reproduce both the current digital video signal and the HD digital video signal with a common cassette tape and a common scanner (drum and heads). Further, as it is produced for home use, the VTR should be a less expensive system. To this end, it is necessary to reduce the bit rate of the digital video signal to thereby decrease the recording data rate and the amount of tape used and reduce the size of the tape cassette.
An apparatus for recording the digital video signal with DCT-based bit-rate reduction has been discussed by Borger et al. in "An Experimental Digital VCR with 40 MM Drum, Single Actuator and DCT-Based Bit-Rate Reduction" in IEEE Transactions on Consumer Electronics, Vol. 34, No. 3, August, 1988, pp. 597-605.
However, in the above-mentioned prior art, no consideration has been made about the compression ratio between the current digital video signal and the HD (high definition) digital video signal, that is to say, about the ratio of the recording data rate between the current digital video signal and the HD digital digital video signal after the bit-rate reduction. Nor has consideration has been made about the multiplexing of the digital video signal with the digital audio signal and the compatibility of the track format. U.S. Pat. No. 4,617,599 assigned to the assignee of the present invention discloses a PCM signal recording/reproducing apparatus which keeps constant the recording format on a recording medium by varying the number of drum revolutions and also the tape speed according to the sampling frequency of the audio signal.